While many of the currently available electronic apparatus have largely increased operational speed, the electronic elements thereof also produce a large quantity of heat. It is very important to timely remove the heat produced by the electronic elements and chips from the electronic apparatus, lest the electronic apparatus should become damaged due to overheating caused by accumulated heat therein.
To properly remove the produced heat, heat sinks or various kinds of thermal modules and cooling fans can be provided on the electronic elements and the chips, so as to cool the electronic elements and chips and to dissipate heat therefrom. Among others, heat pipe is the currently most effective and popular means for heat transfer. A heat pipe can be made of a copper material or an aluminum material to have an internal chamber. A wick structure is formed on an inner surface of the chamber, and a working fluid is provided in the chamber. After the chamber is vacuumed, an open end of the heat pipe is sealed to thereby give the heat pipe a vacuumed and completely closed chamber. The heat pipe can be configured in different shapes, but is most frequently configured as a tube or a flat hollow plate. The wick structure in the heat pipe has significant influence on the heat transfer ability of the heat pipe, particularly for the flat heat pipe, which is also referred to as a vapor chamber. An ideal wick structure must be able to provide strong capillary force while having a small flow resistance. However, these two requirements are opposed to each other in terms of structure. To solve this conflicting condition, the only way is to perform surface modification in order to change the characteristics of the surface of the material. Generally, the surface modification is aimed to change the wick structure for the latter to have wettability and accordingly increased capillary force. One of the most effective methods to modify the material surface for the same to have wettability is to produce a nano-sized microstructure. The nano-sized microstructure can be produced in different processes, including etching process and chemical vapor deposition (CVD) process. In the etching process, a chemical solution is used to corrode the material surface and thereby form a recessed microstructure thereon. However, the etching process has the disadvantages of not easy to control the etching rate and tending to cause environmental pollution. On the other hand, the CVD process can deposit a nano-sized structure on the material surface but not in the micro pores in the wick structure, and therefore fails to achieve the purpose of surface modification.
Taiwan Invention Patent Number I292028 discloses a heat pipe and a method manufacturing the same. The heat pipe includes a hollow tubular enclosure having two sealed ends, a wick structure formed on an inner wall surface of the hollow tubular enclosure and having a hydrophilic coating formed thereon; and a working fluid filling the wick structure and being sealed in the tubular enclosure. The hydrophilic coating can be formed of a material selected from the group consisting of nano-TiO2, nano-ZnO, nano-Al2O3, and any combination thereof, and has a thickness ranged between 10 nm and 200 nm, preferably ranged between 20 nm and 50 nm.
According to Taiwan Invention Patent Number I292028, the tubular enclosure is formed on an outer wall surface with a thermally conductive coating, which can be formed of a material selected from the group consisting of carbon nanotube, nano-copper, nano-aluminum, and copper-aluminum alloy nano thin film; and has a thickness ranged between 10 nm and 500 nm, preferably ranged between 20 nm and 200 nm.
The wick structure includes carbon nano capsules and carbon fibers, and has a thickness ranged between 0.1 mm and 0.5 mm, and preferably ranged between 0.2 mm and 0.3 mm.
And, the method of manufacturing the heat pipe includes the steps of providing a hollow tubular enclosure; forming a wick structure on an inner wall surface of the hollow tubular enclosure; forming a hydrophilic coating on a surface of the wick structure; and vacuum-sealing an adequate quantity of working fluid in the hollow tubular enclosure.
The inner and outer wall surfaces of the hollow tubular enclosure are subjected to a laser texturing process in advance.
The hydrophilic coating is formed through chemical vapor deposition (CVD), plasma enhanced CVD, sputtering deposition, or co-sputtering deposition.
The above-mentioned prior art heat pipe manufacturing method requires equipment and instruments that are highly expensive to inevitably increase the manufacturing cost of the heat pipe, and therefore has the following disadvantages: (1) it can only form deposition on the surface of a workpiece; (2) it is not suitable for mass-production; (3) it requires high manufacturing cost; and (4) it is implemented using expensive equipment.